1. Field of the Invention
The present invention relates to a spur wheel gear for a drive mechanism of a roll, e.g., a suction roll having a stationary suction box and a rotating roll jacket. The spur wheel gear may include a support bracket that supports a gear or driven end of the roll through a self-aligning (self-adjusting) bearing. The gear end may also include, when the roll is a suction roll, a mounting area for coupling an externally mounted suction device to the stationary suction box. The gear end of the roll may be rigidly coupled to an external gear ring that meshes with the drivable pinion driven by a laterally positioned drive shaft. The pinion may engage a first or pinion end of the drive shaft and may be supported by an additional support bearing located adjacent to another self-aligning bearing of the pinion. The additional support bearing may be permitted a predetermined amount of radial play to enable a certain degree of tilt by the pinion.
2. Discussion of Background Information
Spur wheel gears of type generally utilized in the art have been disclosed in, e.g., DE 38 04 225 A1. Known roll types, e.g., deflection adjustment rolls or suction rolls, as utilized in the paper industry, e.g., in water removal presses, glazing rollers, in tissue machines, and the like. Rolls of this kind have a roll jacket that is rotatable around a stationary carrier and/or a stationary suction box.
When rolls of the type discussed above are in operation, if the roll jacket bends under the load, then an external gear ring coupled to the roll jacket, along with an end region of the roll jacket, inclines slightly relative to the gear housing, which cannot be inclined and which is simultaneously used as a support bracket for the entire roller.
Due to the relative tilting of the roll with respect to a pinion, inclination of the external gear ring leads to an edge carrying of the gearing on both sides. This could be avoided by supporting the pinion in the gear housing so that the engagement line of the gearing with the external gear ring runs perpendicular to the bending direction of the roller jacket. However, this condition is difficult to precisely maintain, and moreover, is difficult to maintain for only one respective rotation direction of the roll jacket. Furthermore, the embodiment of the bearing housing would be limited.
In the general spur wheel gear discussed above, the pinion is supported on ball bearings. The tooth flanks, therefore, rest against one another without edge carrying along a common flank line, in accordance with the normal force to be transmitted, and a position of the pinion with respect to the bending direction of the roll jacket can be predefined.
However, a degree of freedom of the pinion must still be limited. Specifically, tilting of the pinion around a central axis of the pinion, i.e., parallel to an engagement line, due to a frictional moment produced by an offset of the pinion axis with respect to the shaft axis driving the pinion. In the prior art spur wheel gear, the tilting occurs through an additional support bearing, provided next to a self-aligning bearing of the pinion, that allows radial play in relation to the pinion so that the pinion tilts into a definite position. The tilting reduces common flank lines, and the linear contact of the tooth flanks turns into a point contact. In this manner, a ball-shaped quality is given to the tooth flanks in a practical manner by a kinematic effect.
The ball shape of the tooth flanks has the advantage of reducing a diagonal load distribution having a high edge compression and limiting the transferrable moment. However, it can only be small since the transferrable power otherwise drops. Thus, the radial play is only selected to be small.
However, a problem occurs in that, due to the additional support bearing next to the self-aligning bearing of the pinion, the spacing of the coupling between the drive shaft and the pinion from the central plane of the self-aligning bearing of the pinion is relatively large. This relatively large spacing causes a diagonal load distribution on the tooth flanks of the pinion since the friction in the geared coupling between the pinion and the pinion drive shaft produces relatively high reaction moments and reaction forces, which are partially supported on the meshing tooth flanks of the pinion.
Further, the pinion tilt occurring during the operation of the roll produces a comparatively large additional deflection of the coupling between the drive shaft and the pinion. When the drive shaft includes a coupling shaft between the pinion and a drive sleeve driven by the roller drive, this additionally results in a relatively large difference of the bending angle of the coupling between the coupling roller and the pinion and between the coupling shaft and the drive sleeve.
When the roll is a suction roll, e.g., generally employed in tissue machines, the prior art devices utilize a complicated routing of a suction line. For example, because the suction occurs on the operator end of the suction roll, i.e., the end opposite the gear end, a number of reroutings are required along with the routing of the pipes to the drive end.
Further, suction rolls generally require a significant number of parts, e.g., an internal bearing and a pipeline through the machine. Further, known suction rolls require a bearing and a suction head on an operator end of the suction roll, as well as bulky collecting conduits.